1. Technical Field
This device relates to improvements in electromagnetic coil driven industrial disk brakes. More particularly, the invention relates to a brake for use with an overhead crane wherein a spring-urged braking armature is selectively pulled away from a multiple disk braking assembly by activation of electromagnetic coils.
2. Description of Prior Art
Prior art devices of this type have used a variety of different brake configurations such as direct current magnetic shoe brakes seen in U.S. Pat. No. 3,322,242 where a pair of opposing brake shoes are pivotally engaged against a drum. These brakes have maintenance problems requiring frequent adjustment and thermal limitations during service.
Caliper disk brakes provide a pair of oppositely disposed braking pads for engaging on either side of a brake disk connected to a crane hoist drive shaft as seen in U.S. Pat. No. 5,582,277.
U.S. Pat. No. 4,067,420 is directed to a disk brake for industrial use having a pair of brake blocks on either side of a brake disk with an electromagnetic release.
U.S. Pat. No. 3,520,386 is also directed to an industrial disk brake having a braking disk with two opposing armatures with attached brake shoes that are urged together against the braking disk by the action of the stack of bellevelle washers bringing the braking assembly liners for engagement with the braking disks. Deactivation of the electromagnetic coil disengages the hereinbefore described braking pads.
U.S. Pat. No. 5,253,738 discloses a safety disk brake for lifts having brake shoes and linings that are spring-urged against a brake disk. An electromagnetic counter force is exerted to lift the brake shoes from the disk releasing same.
Prior art braking assemblies upon which the improvement of the invention is based have a multiple friction plate and thrust braking assembly with a pull brake assembly and a registering armature plate assembly, for example, manufactured by Robin-Meyers, Inc.
Such DC brake assemblies require high voltage initially which has to be switched to low voltage to prevent coils from over heating. This typically results in brake creep which is undesirable.
Applicant's improvement of tuned DC circuit driven by a tuned AC transformer allows the flux in the circuit to decay very rapidly thus closing the brake instantly thus stopping the load instantly which is not possible in prior art brakes of this type.